code: def test_preprocess_data():
      df = pd.read_csv(
          "tests/unit/ml_handlers/data/anomaly_detection.csv"
      )
      preprocessed_df = preprocess_data(df)
      assert len(preprocessed_df) == len(df)
  
file_path: mindsdb/tests/unit/ml_handlers/test_anomaly_detection.py
imports: import time
  import pandas
  from unittest.mock import patch
  from mindsdb_sql import parse_sql
  from tests.unit.executor_test_base import BaseExecutorTest
  from mindsdb.integrations.handlers.anomaly_detection_handler.anomaly_detection_handler import choose_model, preprocess_data
label_desc: Use image node_id 2 for calling a global function with example usage: test_preprocess_data() without return types